With the development of display technology, the flat panel device, such as Liquid Crystal Display (LCD) possesses advantages of high image quality, power saving, thin body and wide application scope. Thus, it has been widely applied in various consumer electrical products, such as mobile phone, television, personal digital assistant, digital camera, notebook, laptop, and becomes the major display device.
The Thin Film Transistor (TFT) liquid crystal display device is the most common display device at present. The Thin Film Transistor liquid crystal display device controls the input of the display data signal with the thin film transistors, and thus to control the image display. Specifically, each liquid crystal pixel dot on the liquid crystal display device is driven by the thin film transistor integrated behind it. With the drive of the thin film transistor, the high speed, high brightness, high contrast display screen information can be achieved. The electrical property of the thin film transistor will drift as time goes by. The reason is that more defects exist at the interface of the amorphous silicon and the silicon nitride (SiNx). The long time bias will lead to the charge accumulation at the interface of the amorphous silicon and the silicon nitride. The electrical field formed by these charges will overlap with the gate voltage to result in the threshold voltage (Vth) drift of the thin film transistor, and then the electrical property of the thin film transistor drifts. Ultimately, it results in the drift of the voltage-transmission rate curve (V-T curve) of the panel and influences the display quality.
At present, the Gamma adjustment and the Flicker adjustment are required to perform before the TFT-LCD leaves the factory. The gamma value of the gamma curve of the TFT-LCD is adjusted to be the target gamma value (2.2) and the common voltage (Vcom) value is adjusted to be the best Vcom for making blink values lowest to obtain a set of a gamma datum and a Vcom datum. Specifically, for some gray scale, an initial voltage is first outputted. Then the pixel brightness is tested to judge whether the relationship of the two satisfies the 2.2 power exponent relation. If it is not satisfied, the initial voltage is adjusted, and then the pixel brightness is tested to judge whether the relationship of the two satisfies the 2.2 power exponent relation, again until the final voltage that makes the relationship of the two satisfy the 2.2 power exponent relation is found. The aforesaid process is repeated to find out the final voltage of the preset certain gray scale to obtain the gamma data of making the gamma value of the gamma curve of the TFT-LCD is equal to 2.2.
However, after the adjusted liquid crystal display device has been used for a period of time, the electrical property of the thin film transistor will drift as time goes by, and then the gamma curve deviates from gamma 2.2, and Vcom value deviates from the best Vcom to ultimately lead to that the display result is getting worse. Namely, the longer the liquid crystal display device is used, the worse the display result becomes. Consequently, it is required to provide a method to maintain the liquid crystal display device with the high quality display.